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Versions: (draft-farrel-pce-vendor-constraints) 00 01 02 03 04 05 06 07 08 09 10 11 RFC 7150

Network Working Group                                       Fatai Zhang
Internet-Draft                                                   Huawei
Intended status: Standards Track                              A. Farrel
                                                       Juniper Networks

Expires: October 16, 2013                                April 16, 2013


            Conveying Vendor-Specific Constraints in the Path
                      Computation Element Protocol

                 draft-ietf-pce-vendor-constraints-09.txt


Abstract

   The Path Computation Element Protocol (PCEP) is used to convey path
   computation requests and responses between Path Computation Clients
   (PCCs) and Path Computation Elements (PCEs), and also between
   cooperating PCEs. In PCEP the path computation requests carry
   details of the constraints and objective functions that the PCC
   wishes the PCE to apply in its computation.

   The mechanisms defined for indicating objective functions include
   the capability to convey vendor-specific objective functions. This
   document defines a facility to carry vendor-specific constraints in
   PCEP.


Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
   groups may also distribute working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time. It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html



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Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document. Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", "OPTIONAL" in this
   document are to be interpreted as described in RFC-2119 [RFC2119].


1. Introduction

   A Path Computation Element (PCE) is an entity (component,
   application or network node) that is capable of computing a network
   path or route based on a network graph and applying computational
   constraints. An architecture for the use of PCEs is defined in
   [RFC4655].

   The Path Computation Element Protocol (PCEP) is defined in [RFC5440]
   to exchange path computation requests and responses between Path
   Computation Clients (PCCs) and PCEs. It is also used between
   cooperating PCEs.

   Path computations performed by a PCE depend on a set of constraints
   indicated by the PCC. These constraints include the end points of
   the path to compute (source and destination), and may include other
   simple constraints such as bandwidth requirements and metric maxima
   (for example, a maximum threshold for the hop count or the TE metric
   of the computed path).

   The PCE also needs to use an objective function to qualify the path
   it selects as meeting the requirements of the PCC. The PCE may have a
   default objective function, but the PCC can also indicate which
   objective function it wants applied by placing an Objective Function
   object in the path computation request message [RFC5541]. A core set


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   of objective functions to be supported in PCEP messages is defined in
   the base PCEP requirements [RFC4657], and [RFC5541] defines each of
   these functions as an abstract formula.

   The registry of codepoints used to indicate objective functions is
   managed by IANA and new assignments can be made according to "IETF
   Review" and "First Come First Served" policies [RFC5226]. PCE
   implementations may also choose to offer proprietary, vendor-specific
   objective functions, and there is scope for this within the
   codepoint registry created by [RFC5541] using the codepoints that are
   flagged as "Reserved for Private Use."

   Proprietary objective functions may operate on non-standard
   constraints or metrics. The PCEP Metric Object defined in [RFC5440]
   has scope for the definition of new, standardized metrics, but no
   facility for the definition of vendor-specific metrics. At the same
   time, there is no mechanism in PCEP for carrying other, more complex,
   vendor-specific constraints.

   This document defines a new PCEP object, the Vendor Constraints
   object that can be used to carry arbitrary, proprietary constraint
   information.

   This document also defines a new PCEP TLV, the VENDOR-CONSTRAINT-TLV
   that can be used to carry arbitrary constraint information within any
   PCEP object that supports TLVs.


2. Procedures for The Vendor Constraints Object

   A PCC that wants to convey proprietary or vendor-specific
   constraints or metrics to a PCE does so by including a Vendor
   Constraints object in the PCReq message. The contents and format of
   the object are described in Section 4, but it is important to note
   that the object includes an Enterprise Number that is a unique
   identifier of an organization responsible for the definition of the
   content and meaning of the object.

   A PCE that receives a PCReq message containing a Vendor Constraints
   object MUST act according to the P-bit in the object header. That is,
   if the P flag is set, the object MUST be treated as mandatory and the
   request is either processed using the contents of the object or
   rejected as defined in [RFC5440]. If the P flag is clear, then as
   defined in [RFC5440], the object MAY be used by the PCE or MAY be
   ignored. The PCC sets the P flag according to how it wishes the
   request to be processed.

   The PCE determines how to interpret the Vendor Constraints object by


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   examining the Enterprise Number it contains. If the Enterprise
   Number is unknown to the PCE, it MUST treat the Vendor Constraints
   object as unknown and handle it as described in [RFC5440] according
   to the setting of the P flag (see also Section 2.1).

   The Vendor Constraints object is OPTIONAL in a PCReq message.
   Multiple instances of the object MAY be used on a single PCReq
   message and each MUST be treated according to its P-bit setting. The
   object can be present in two places within the PCReq message to
   enable it to apply to a single path computation request or to a set
   of synchronized requests. This usage mirrors the usage of the
   Objective Function object [RFC5541]. Thus, the PCReq message based
   on [RFC6006] is encoded as follows using the syntax described in
   [RFC5511].

        <PCReq Message> ::= <Common Header>
                            [<svec_list>]
                            <request-list>

        where

            <svec-list> ::= <SVEC>
                            [<OF>]
                            [<GC>]
                            [<XRO>]
                            [<metric-list>]
                            [<vendor-constraint-list>]
                            [<svec-list>]

            <metric-list> ::= <METRIC>
                              [<metric-list>]

            <vendor-constraint-list> ::= <VENDOR-CONSTRAINT>
                                         [<vendor-constraint-list>]

            <request-list> ::= <request>
                               [<request-list>]

            <request>::= <RP>
                         [<vendor-constraint-list>]
                         <end-point-rro-pair-list>
                         [<LSPA>]
                         [<BANDWIDTH>]
                         [<metric-list>]
                         [<OF>]
                         [<RRO>]
                         [<IRO>]
                         [<LOAD-BALANCING>]


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        where

            <end-point-rro-pair-list> ::= <END-POINTS>
                                          [<RRO-List>]
                                          [<BANDWIDTH>]
                                          [<vendor-constraint-list>]
                                          [<end-point-rro-pair-list>]

            <RRO-List> ::= <RRO> [<BANDWIDTH>] [<RRO-List>]

            <metric-list> ::= <METRIC> [<metric-list>]

   The Vendor Constraints object is included in a PCRep message in
   exactly the same way as any other object as defined in [RFC5440].

2.1. Backward Compatibility

   A legacy implementation that does not recognize the Vendor Constraint
   object will act according to the procedures set out in [RFC5440]. If
   the P flag is set in the object, the message will be rejected using a
   PCErr message with an Error Type of 3 ("Unknown Object"). If the P
   flag is not set, the object can safely be ignored by the recipient.


3. Procedures for The Vendor Constraints TLV

   The Vendor Constraints TLV may be used to indicate a vendor-specific
   constraint that applies to a specific PCEP object by including it in
   the object.

   The PCE determines how to interpret the Vendor Constraints TLV by
   examining the Enterprise Number it contains. If the Enterprise
   Number is unknown to the PCE, it MUST treat the Vendor Constraints
   TLV as unknown and handle it as described in [RFC5440] (see also
   Section 3.1).

   Further specifications are needed to define the position and meaning
   of the Vendor Constraints TLV for specific PCEP objects.

3.1. Backward Compatibility

   A legacy implementation that does not recognize the Vendor Constraint
   TLV in an object will act according to the procedures set out in
   [RFC5440]. As described in Section 7.1 of [RFC5440], unrecognized
   TLVs MUST be ignored.





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4. Protocol Elements

   The Vendor Constraints object and TLV conform to the format for PCEP
   objects and TLVs defined in [RFC5440].

   VENDOR-CONSTRAINT Object-Class is <TBD1> to be assigned by IANA.

   VENDOR-CONSTRAINT Object-Type 1

   VENDOR-CONSTRAINT-TLV Type is <TBD2> to be assigned by IANA.

   The format of the VENDOR-CONSTRAINT object and the
   VENDOR-CONSTRAINT-TLV body is as shown in Figure 1.


      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                       Enterprise Number                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                 Enterprise-Specific Information               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 1 : Format of the Vendor Constraints Object

   Enterprise Number

     A unique identifier of an organization encoded as a 32-bit integer.
     Enterprise Numbers are assigned by IANA and managed through an IANA
     registry [RFC2578].

   Enterprise-Specific Information

     The detailed enterprise-specific constraint information carried by
     the object. The format and interpretation of this information is a
     matter for the enterprise identified by the Enterprise Number. Such
     formats and interpretation may be published by the enterprise
     (possibly through an informational RFC or through commercial
     documentation) so that PCCs or PCEs that are not part of the
     organization can use the information.


5. IANA Considerations

   IANA maintains a registry of PCEP parameters called the "Path
   Computation Element Protocol (PCEP) Numbers".




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5.1. New PCEP Object

   IANA is requested to make an allocation from the "PCEP Objects"
   sub-registry as follows. The value here is suggested for use by IANA.

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   Object-Class Value     Name                               Reference
   TBD1                   VENDOR-CONSTRAINT                  [This.I-D]
              Object-Type
                0: Unassigned
                1: Vendor-Specific Constraints               [This.I-D]
                2-255: Unassigned

5.2. New PCEP TLV

   IANA is requested to make an allocation from the "PCEP TLV Type
   Indicators" sub-registry as follow.

   Value       Description                                   Reference
   TBD2        VENDOR-CONSTRAINT-TLV                         [This.I-D]


6. Management Considerations

   This section follows the guidance of [RFC5706] and [RFC6123].

6.1. Control of Function and Policy

   A PCEP implementation SHUOLD allow configuring of various parameters
   as described in [RFC5440]. A PCC implementation that uses vendor-
   specific constraints MAY make the use of these constraints
   configurable either across the whole PCC, per PCE that the PCC uses,
   or per path computation request. A PCE that supports vendor-specific
   constraints MAY make the support of these constraints configurable,
   and MAY allow configuration of policies for the use of the
   constraints.

6.2. Information and Data Models

   A PCEP MIB module is defined in [PCE-MIB] that describes managed
   objects for modeling of PCEP communications.

   It is NOT RECOMMENDED that standard MIB modules are extended to
   include detailed information about the content of the Vendor


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   Constaints object. However, the standard MIB module MAY be extended
   to report the use of the Vendor Specific object and the Enterprise
   Numbers that the objects contain.

6.3. Liveness Detection and Monitoring

   This document makes no change to the basic operation of PCEP and so
   there are no changes to the requirements for liveness detection and
   monitoring set out in [RFC4657] and [RFC5440].

6.4. Verifying Correct Operation

   This document makes no change to the basic operation of PCEP and so
   there are no changes to the requirements or techniques for
   monitoring the correct operation of the protocol out in [RFC4657]
   and [RFC5440].

   Note that "correct operation" in this context referes to the
   operation of the protocol itself, and not to the operation of the
   computation algorithms which are out of scope for all PCEP work.

   Mechanisms for verifying the correct operation of computation
   algorithms might involve comparing the results returned by more than
   one PCE. Scope for this might be limited by the use of vendor
   constraints unless multiple PCEs support the same set of constraints.

6.5. Requirements on Other Protocols and Functional Components

   This document does not place any new requirements on other network
   components or protocols. However, it may be beneficial to consider
   whether a PCE should advertise the enterprise numbers and vendor
   constraints it supports. This advertisement could be within PCE
   Discovery ([RFC5088], [RFC5089]) or through extensions to PCEP
   [RFC5440].

   Extensions for discovery and advertisement are outside the scope of
   this document.

6.6. Impact on Network Operation

   The availability of vendor constraints in PCEP messages may
   facilitate more complex and detailed path computations that may
   enhance the way in which the network is operated.

   On the other hand, the presence of additional vendor-specific
   information in PCEP messages may congest the operation of the
   protocol especially if the PCE does not support the constraints
   supplied by the PCC. Thus, a PCC SHOULD monitor the capabilities of


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   a PCE either by discovery mechanisms as described in Section 6.5, or
   through the receipt of negative responses. A PCC SHOULD NOT include
   vendor constraints in a PCReq message to a PCE that it believes does
   not support the constraints and that will not forward the request to
   some other PCE that does support the constraints.


7. Security Considerations

   The protocol extensions defined in this document do not
   substantially change the nature of PCEP. Therefore, the security
   considerations set out in [RFC5440] apply unchanged.

   Operators should note that an attack on PCEP may involve making PCEP
   messages as large as possible in order to consume bandwidth and
   processing power. The Vendor Constraints object may provide a
   mechanism for this type of attack. It may be protected against by
   using the authentication and integrity procedures described in
   [RFC5440].


8. References

8.1. Normative References

   [RFC2119] S. Bradner, "Key words for use in RFCs to indicate
             requirements levels", RFC 2119, March 1997.

   [RFC5440] Vasseur, J.P., Le Roux, J.L., Ayyangar, A., Oki, E.,
             Ikejiri, A., Atlas, A., Dolganow, A., "Path Computation
             Element (PCE) communication Protocol (PCEP)", RFC 5440,
             March 2009.

   [RFC5511] Farrel, A., "Reduced Backus-Naur Form (RBNF): A Syntax to
             Form Encoding Rules in Various Routing Protocol
             Specifications", RFC 5511, April 2007.

   [RFC6006] Q. Zhao, et al., "Extensions to the Path Computation
             Element Communication Protocol (PCEP) for Point-to-
             Multipoint Traffic Engineering Label Switched Paths", RFC
             6006, September 2009.

8.2. Informative References

   [RFC2578] McCloghrie, K., Perkins, D., and J. Schoenwaelder,
             "Structure of Management Information Version 2 (SMIv2)",
             STD 58, RFC 2578, April 1999.



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   [RFC4655] Farrel, A., Vasseur, J.P., Ash, J., "Path Computation
             Element (PCE) Architecture", RFC 4655, August 2006.

   [RFC4657] Ash, J. and J. Le Roux, "Path Computation Element (PCE)
             Communication Protocol Generic Requirements", RFC 4657,
             September 2006.

   [RFC5088] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
             "OSPF Protocol Extensions for Path Computation Element
             (PCE) Discovery", RFC 5088, January 2008.

   [RFC5089] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
             "IS-IS Protocol Extensions for Path Computation Element
             (PCE) Discovery", RFC 5089, January 2008.

   [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
             IANA Considerations Section in RFCs", BCP 26, RFC 5226,
             May 2008.

   [RFC5541] Le Roux, JL., Vasseur, JP., and Y. Lee, "Objective
             Function Encoding in Path Computation Element
             Communication and Discovery protocols", RFC 5541, June
             2009.

   [RFC5706] Harrington, D., "Guidelines for Considering Operations and
             Management of New Protocols and Protocol Extensions", RFC
             5706, November 2009.

   [RFC6123] Farrel, A., "Inclusion of Manageability Sections in Path
             Computation Element (PCE) Working Group Drafts", RFC 6123,
             February 2011.

   [PCE-MIB] Stephan, E. and K. Koushik, "PCE Communication Protocol
             (PCEP) Management Information Base", draft-ietf-pce-pcep-
             mib, work in progress.


9. Acknowledgements

   Thanks to Meral Shirazipour, Ramon Casellas, Cyril Margaria, and
   Dhruv Dhody for review and comments.


10. Authors' Addresses

   Adrian Farrel
   Juniper Networks
   EMail: adrian@olddog.co.uk


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   Fatai Zhang
   Huawei Technologies
   Email: zhangfatai@huawei.com


11. Contributor

   Greg Bernstein
   Grotto Networking
   EMail: gregb@grotto-networking.com








































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